Evaluation of the Roche Antigen Rapid Test and a Cell Culture-Based Assay compared to rRT- PCR for the detection of SARS CoV-2: a contribution to the discussion about SARS CoV-2 diagnostic tests and contagiousness

Abstract Background: The most sensitive method to detect SARS-CoV-2 relies on rRT-PCR; however, viral RNA can be detected weeks/months after clinical resolution. Since rRT-PCR cannot discern between non- and infectious virus, it is unclear whether the presence of viral RNA after recovery reflects infectious SARS-CoV-2. However, recent studies suggest a positive correlation between antigen rapid tests (Ag-RDT) and virus isolation that is more suited to assess contagiousness. Objectives: To assess the utility of SARS CoV-2 diagnostic tests in different settings we evaluated the performance of Ag-RDT-based and a cell-culture-based SARS-CoV-2 assay in comparison to rRT-PCR. Study design: A total of 61 Nasopharyngeal-Swabs tested positive by cobas® SARS-CoV-2 rRT-PCR were in parallel evaluated with the Roche Ag-RDT and a cell culture-based assay to detect SARS-CoV-2. Results: SARS-CoV-2 was successfully isolated in 51/61 samples corresponding to 83.6%, which was 97.3% or 96.2% when considering samples with E-gene Ct-value Conclusions: Our results support the use of the Roche Ag-RDT to detect SARS-CoV-2 exposure in large scale populations. However, it is recommended to use rRT-PCR, potentially in conjunction with cell culture-based SARS-CoV-2 assay, to support clinicians in making decisions regarding fragile patient groups.